Fgf8 expression in the anterior developing mouse brain induces anterior identity marker expression (anteriorization). The Fgf8 receptor is uniformly expressed in the brain. Which one of the following experiments best demonstrates this fact?
1
Transgenic overexpression of Fgf8 in the posterior of the developing mouse brain causes anteriorization at both ends of the brain.
2
Transgenic overexpression of Fgf8 receptor in the posterior of the developing mouse brain causes anteriorization at both ends of the brain.
3
Grafting the anterior portion of an Fgf8 null developing mouse brain into the posterior of another developing mouse brain causes the recipient's brain to be anteriorized at both ends.
4
Transgenic overexpression of Fgf8 in the posterior of the developing mouse brain results in no anteriorization.